1. Field of the Invention
This invention relates to a shift system for a boat propulsion unit.
2. Description of the Related Art
Conventionally, the boat propulsion unit is provided with a shift system for controlling forward, neutral, and reverse operation of a boat.
This shift system includes a normal turn gear and a reverse turn gear meshing with right and left sides of a drive gear coupled to a drive shaft which extends from an engine. A propeller shaft is fixed to a propeller and a dog clutch shift-transmits the rotation of the normal or reverse turn gear to the propeller shaft. A shift rod is used to slide the dog clutch to right and left directions.
The dog clutch is driven with a cam fixed to the fore-end of the shift rod. When the shift rod is turned in the normal turn direction, the dog clutch moves toward the left, so that the cogs of the dog clutch engage with the cogs of the normal turn gear. Rotation of the drive shaft is transmitted through the drive gear and the normal turn gear to the propeller shaft. When the shift rod is turned in the reverse turn direction, the dog clutch moves toward the right, so that the cogs of the dog clutch engage with the cogs of the reverse turn gear. Rotation of the drive shaft is transmitted through the drive gear and the reverse turn gear to the propeller shaft (See e.g. JP-A-Hei 11-334694 (pp. 1-6, FIGS. 1-8)).
In the shift system, for example, the turn of the shift rod is made by actuating a shift actuator by manipulating a remote control shift lever, as shown in FIG. 11A. The remote control shift lever is tilted forward from the neutral position (N) to the forward position (F), or from the neutral position (N) rearward to the reverse position (R). The shift output member of the shift actuator moves from the neutral position (N) to the forward position (F), or from the neutral position (N) to the reverse position (R) is controlled to be in proportion to the operation amount of the remote control shift lever.
On the other hand, as for the actual shift position of the shift system (see FIG. 11B), even when the remote control shift lever of the shift system is tilted forward by a specified angle from the neutral position (N), the dog clutch actually does not move until the shift lever angle reaches a specified angle (F0). When the specified angle (F0) is reached, the dog clutch moves to the forward position (F) and stops moving before the remote control shift lever comes to the forward position (F). Likewise, when the remote control shift lever is tilted rearward from the neutral position (N) by a specified angle, the dog clutch does not move until the shift lever angle reaches a specified angle (R0). When the specified angle (R0) is reached, the dog clutch moves to the reverse position (R) and stops moving before the remote control shift lever comes to the reverse position (R).
As described above, driving the shift actuator from a distance through the remote control shift lever operation, depending on the manner of action of the shift actuator corresponding to the remote control shift lever operation, may change the ease of use, or the response of, the dog clutch engagement and may give inconsistent feeling in the shift operation.